Messages in this thread Patch in this message | | | Date | Wed, 16 Mar 2022 21:48:06 +0100 | From | Peter Zijlstra <> | Subject | Re: failure to boot after dc6e0818bc9a "sched/cpuacct: Optimize away RCU read lock" |
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On Wed, Mar 16, 2022 at 01:43:24PM -0400, J. Bruce Fields wrote: > One of my test VMs has been failing to boot linux-next recently. I > finally got around to a bisect this morning, and it landed on the below. > > What other information would be useful to debug this?
A more recent -next should have this commit in it:
commit f2aa197e4794bf4c2c0c9570684f86e6fa103e8b Author: Chengming Zhou <zhouchengming@bytedance.com> Date: Sat Mar 5 11:41:03 2022 +0800
cgroup: Fix suspicious rcu_dereference_check() usage warning
task_css_set_check() will use rcu_dereference_check() to check for rcu_read_lock_held() on the read-side, which is not true after commit dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock"). This commit drop explicit rcu_read_lock(), change to RCU-sched read-side critical section. So fix the RCU warning by adding check for rcu_read_lock_sched_held().
Fixes: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock") Reported-by: Linux Kernel Functional Testing <lkft@linaro.org> Reported-by: syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Tejun Heo <tj@kernel.org> Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Link: https://lore.kernel.org/r/20220305034103.57123-1-zhouchengming@bytedance.com
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 1e356c222756..0d1ada8968d7 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -450,6 +450,7 @@ extern struct mutex cgroup_mutex; extern spinlock_t css_set_lock; #define task_css_set_check(task, __c) \ rcu_dereference_check((task)->cgroups, \ + rcu_read_lock_sched_held() || \ lockdep_is_held(&cgroup_mutex) || \ lockdep_is_held(&css_set_lock) || \ ((task)->flags & PF_EXITING) || (__c))
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